Preparation of unsaturated acid esters from unsaturated aldehydes



United States Patent Ofiice 3,358,015 Patented Dec. 12, 1967 3,358,015 PREPARATION OF UNSATURATED ACID ESTERS FROM UNSATURATED ALDEHYDES Irwin Schlossman, New York, N.Y., and Charles N. Winnick, Bergen County, N.J., assignors to Halcon International, Inc., a corporation of Delaware No Drawing. Filed Nov. 12, 1963, Ser. No. 323,099 5 Claims. (Cl. 260486) This invention relates to processes for the production of carboxylic esters from corresponding aldehydes and alcohols, and more particularly to the production of an unsaturated ester from a corresponding unsaturated aldehyde by reaction of the latter with an organic hydroperoxide in the presence of a redox material dispersed in alcohol. It relates especially to preparing methyl methacrylate from methacrolein, methanol, t-butyl hydroperoxide and ferrous chloride and/or ferric chloride.

The art has appreciated the desirability of being able to produce acrylic esters from the corresponding acroleins and alcohols. However, because of undesirable side reactions, it has been necessary, generally, to resort to expensive indirect methods for preparing such esters. A major problem is the tendency of the initial acrolein as well as the acrylic ester product to undergo polymerization to polymeric or co-polymeric products in an oxidizing environment making isolation of the monomeric esters substantially impossible. Another problem is the tendency of the usual oxidation systems to attack points of unsaturation instead of or in addition to the aldehyde group. Attempts have been made to avoid these difficulties by using a very dilute system or by using complicated procedures and/or by using costly reaction systems, all of which leave much to be desired. Accordingly, the art is confronted by the problem of providing processes for producing vinylic esters from corresponding unsaturated aldehydes in a more convenient and/ or economic manner and especially acrylic and substituted esters from the corresponding acroleins.

' The discoveries associated with the invention and relating to the solution of the above problems, and the objects achieved in accordance with the invention as set forth herein include the provision of:

The process for preparing an ester from an aldehyde which comprises reacting an organic hydroperoxide with an aldehyde in the presence of a non-tertiary alkanol and a redox material of an element from the group of elements having an atomic number of 22 to 28, 50, 58 and 82 inclusive to form the alkanol ester of the acid corresponding to the aldehyde, the ester being recovered as product;

Such a process wherein the redox material contains iron in solution;

Such a process wherein the aldehyde is an alpha, beta-ethylenic aldehyde and the alkanol is primary and contains one to twelve carbon atoms;

Such a process wherein methacrolein and t-butylhydroperoxide are reacted in the presence of methanol and the product is methyl methacrylate;

Such a process carried out'in the presence of ferrous chloride; 1 1

Such a process carried out in the presence of ferric chloride;

Such a process carried out in the presence of ferric and ferrous chloride;

Such a process carried out in the presence of ferrous bromide;

Such a process carried out in the presence of ferric bromide;

Such a process carried out in the presence of ferric and ferrous bromide;

Such a process wherein the reaction mixture contains substantially stoichiometric amounts of the hydroperoxide and the aldehyde, and an excess of the alkanol;

Such a process using a non-primary (i.e. secondary or tertiary) hydroperoxide with methacrolein and methanol, and an iron redox material in solution in the reaction mixture whereby methyl methacrylate ester is produced;

Such a process wherein tertiary-butylhydroperoxide is used at a temperature in the range of about 50 to +150 0;

Such a process wherein an iron salt is used an amount in the range of 0.05 to 2.0 equivalents per equivalent of hydroperoxide;

Such a process wherein the iron salt is used in an amount in the range of 0.1 to 0.5 equivalent per equivalent of hydroperoxide;

Such a process wherein the alkanol is methanol and a cobtalt redox material is used and methyl methacrylate is recovered as product;

Such a process wherein a manganese material is used with methacrolein and methanol; 7

Such a process wherein a chromium redox material is used with methacrolein and methanol;

Such a process wherein a tin redox material is used with methacrolein and methanol;

And other objects which will be apparent as details or embodiments of the invention are set forth hereinafter.

In order to indicate still more fully the nature of the present invention, the following examples of typical procedures are set forth in which parts and percents mean parts and percents by weights, respectively, unless otherwise indicated, it being understood that these examples are presented as illustrative only and they are not intended to limit the scope of the invention.

EXAMPLE I Methacrolein (7.5 g., 0.107 mol) is dissolved in a mixture containing 10.0 g. FeCl .4H O (0.05 mol) and 50 cc. of methanol. The mixture is stirred and the temperature is adjusted to 5 C. Then t-butylhydroperoxide (12.5 g., 0.10 mol) is added slowly, the temperature rising to 15 C. The temperature of the reaction mixture is then allowed to rise to and remain at room temperature (25 C.) for the next 30 minutes. The resulting mixture is analyzed (by gas chromatography); methacrolein conversion is 60% and the selectively to methyl methacrylate is 63 mol percent.

Any convenient method of analysis may be used.

The ester is recovered by fractional distillation and purified, in known manner. The ester-methanol azeotrope is obtained, and then the ester is separated therefrom, e.g. by extraction and/or distillation.

EXAMPLE II Following the procedure of Example I, except that 8.1 g. (0.05 mol) of FeCl is used in place of the ferrous chloride, methacrolein conversion is and the methylmetharcylate selectivity is 42 mol percent. The bromide gives; similar results, i

EXAMPLE III a Following the procedure of Example I except that 7.9 g. (0.4 mol) of FeCl .4H O and 9.7 g. (0.6 mol) of FeCl is used, in place of 10.0 g. if FeCl 4H O, methacrolein conversion is 53% and the selectivity to methylmethacrylate is 77 mol percent. The bromides give similar results.

Following the above procedure but using any one of the redox agents P-bCl CeCl MnCl TiCl CrBr or vanadium acetate, the same ester is obtained.

In the present invention, organic hydroperoxides are employed as oxidizing agents. T-butylhydroperoxide gives particularly outstanding results. Secondary or tertiary hydroperoxides generally are desirable. Illustrative hydroperoxides can be represented generally by the formula ROOH where R is an alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aralkyl, hydroxyalkyl, hydroxycycloalkyl, hydroxyaralkyl, and the like group having about 2 to 20 carbon atoms. Specific organic hydroperoxides are cumene hydroperoxide, cyclohexyl hydroperoxide, l-hydroxy-cyclohexyl hydroperoxide, cyclohex-Z-enyl hydroperoxide, and the like. Mixtures thereof can be used.

The process of the invention is particularly suitable for reacting unsaturated aldehydes for producing the corresponding monomeric esters, especially aldehydes and esters such as acrylic esters and alpha substituted acrylic esters which have a strong tendency to undergo polymerization. Aldehydes having up to 20 or more carbon atoms in the molecule may be used. The process may be applied to such compounds wherein the unsaturation is in any location in the molecule, but the alpha, beta-ethylenic aldehydes are especially important. The aldehydes may be substituted by hydroxy, ether, carboxylic acil, carboxylic acid ester, keto, nitro, and the like groups, or halogen atoms.

The reaction is carried out by adding an organic hydroperoxide or mixture of such hydroperoxides and a redox agent to a solution of an aldehyde such as an alpha, betaethylenic aldehyde in the appropriate reactive primary or secondary alkanol, for example, methanol, ethanol, or other non-tertiary alcohol having up to about 12 carbon atoms in the molecule. Ferrous or ferric ion is a preferred redox agent, and it can be introduced by adding ferrous or ferric chloride or other soluble iron salt or salts to the reaction mixture; chlorides and bromides are the preferred salts. Other known redox agents which can be used instead of or together with the ferrous or ferric ions in the new process include cobaltous, manganous, stannous, cerous, nickelous, plumbous, titanous, chromous, vanadous and the like ions in solution, or mixtures thereof. These metals have atomic numbers 22 to 28, 50, 5'8 and 82.

The redox agent or mixtures thereof can be employed in stoichiometric amounts relative to the hydroperoxide or in excess thereof, e.g. up to about double the amount. However, less than stoichiometric amounts are operable and generally preferable. In general at least 0.05 equivalent of redox agent or agents per equivalent of hydroperoxide is used; a desirable range is 0.1 to 0.5 equivalent of agent per equivalent of hydroperoxide.

The redox agents may be employed in any one of their valance states. For example, equally good results are obtained with either ferrous or ferric chloride. An acidic environment is sometimes desirable, and it is achieved by adding a small amount of sulfuric or hydrochloric or other strong acid to the reaction mixture. A redox couple may be employed, for example, ferrous-ferric or 60- balt-ous-cobaltic, and the like, or a mixed couple such as cobaltous-ferric, man-ganous-stannic and the like.

While chlorides and bromides are preferred, compounds containing other anions may be employed in practicing this invention to produce the esters.

The concentration of the aldehyde or aclolein in the reaction mixture may be in the range of 1 to 50% by weight, preferably in the range of to The reaction temperature may be from 50 C. to +150 C., desirably 0 to 100 C., and preferably in the range of room temperature or somewhat below up to about 60 C. The pressure may be atmospheric, or above or below,

and the reaction time may be in the range. of. 10. minutes.

to 6 hours, and desirably 0.5 to- 3 hours. For many runs, a one hour reaction time is suitable.

The ratio of the hydroperoxide is in the range of 0.1 to 2 mols per mol of the acrolein, preferably 0.5 to 1.0.

The process may be carried out batchwise, or in an intermittent or continuous manner. As to the latter, the reaction may be carried out in an elongated reaction zone such as a tube or a tower or a plurality of reactors connected in series, and the hydroperoxide may be introduced at space points along the path of flow of the solution or mixture.

In view of the foregoing disclosures, variations and modifications thereof will be apparent to one skilled in the art and it is intended to include within the invention all such variations and modifications except as do not come within the scope of the appended claims.

What is claimed is:

I 1. A process for the production of an organic ester which comprises: forming a reaction mixture which contains (1) an organic peroxide, (2) an alpha-beta-ethylenic aldehyde, (3) a non-tertiary alkanol having up to 12 carbon atoms per molecule and (4) a red-ox agent consisting essentially of at least one soluble ion selected from the group consisting of ferric and ferrous; said reaction mixture containing from 1 to 50% by weight of said aldehyde, a ratio of 0.1 to 2 moles per mole of hydroperoxide per mole of aldehyde, and 0.05 to 2 equivalents of said redox agent per equivalent of hydroperoxide; said reaction mixture being substantially free of copper ions; reacting said mixture at a temperature of -50 to C. to form an alk-anol ester corresponding to said aldehyde; and recovering said ester as product.

2. The process of claim 1 wherein said organic hydroperoxide is t-butyl hydroperoxide.

3. The process of claim 1 wherein said alkanol is methanol.

4. The process of claim 1 wherein said redox agent is a ferrous ion.

5. A process for the production of methylmethacrylate which comprises: forming a reaction mixture which contains (1) t-butyl hydroperoxide, (2) 'methylacrolein, (.3) methanol and (4) a redox agent. consisting of soluble ferric and ferrous ions; said reaction mixture containing 1 to 50% by weight of saidmethacrolein, 0.1 to 2 moles per mole of t-butyl hydroperoxide per mole of methacrolein, and 0.05 to 2 equivalents of said redox agent per equivalent of. hydroperoxide; said reaction mixture being substantially free of copper ions; reacting said mixture to form methylmethacrylate and recovering said methylmethacrylate as a product.

References Cited UNITED STATES PATENTS 1/ 1963 Castro et a1. 260-486 OTHER REFERENCES Walling, Free Radicals in Solution, John Wiley & Sons, Inc. (1957), p. 427 relied upon. 

1. A PROCESS FOR THE PRODUCTION OF AN ORGANIC ESTER WHICH COMPRISES: FORMING A REACTION MIXTURE WHICH CONTAINS (1) AN ORGANIC PEROXIDE, (2) AN ALPHA-BETA-ETHYLENIC ALDEHYDE, (3) A NON-TERTIARY ALKANOL HAVING UP TO 12 CARBON ATOMS PER MOLECULE AND (4) A REDOX AGENT CONSISTING ESSENTIALLY OF AT LEAST ONE SOLUBLE ION SELECTED FROM THE GROUP CONSISTING OF FERRIC AND FERROUS; SAID REACTION MIXTURE CONTAINING FROM 1 TO 50% BY WEIGHT OF SAID ALDEHYDE, A RATIO OF 0.1 TO 2 MOLES PER MOLE OF HYDROPEROXIDE PER MOLE OF ALDEHYDE, AND 0.05 TO 2 EQUIVALENTS OF SAID REDOX AGENT PER EQUIVALENT OF HYDROPEROXIDE; SAID REACTION MIXTURE BEING SUBSTANTIALLY FREE OF COPPER IONS; REACTING SAID MIXTRUE AT A TEMPERATURE OF -50 TO 150*C. TO FORM AN ALKANOL ESTER CORRESPONDING TO SAID ALDEHYDE; AND RECOVERING SAID ESTER AS PRODUCT. 